www.nmletters.org Analysis of Nanof luids as Cutting Fluid in Grinding EN-31 Steel V. Vasu 1,∗ , K. Manoj Kumar 2,∗ (Received 13 August 2011; accepted 22 September 2011; published online 3 November 2011.) Abstract: Grinding requires high specific energy which develops high temperatures at wheel work piece interface. High temperatures impair work piece quality by inducing tensile residual stress, burn, and micro cracks. Control of grinding temperature is achieved by providing effective cooling and lubrication. Conven- tional flood cooling is often ineffective due to enormous heat generation and improper heat dissipation. This paper deals with an investigation on using TRIM E709 emulsifier with Al2O3 nanoparticles to reduce the heat generated at grinding zone. An experimental setup has been developed for this and detailed comparison has been done with dry, TRIM E709 emulsifier and TRIM E709 emulsifier with Al2O3 nanoparticles in grinding EN-31 steel in terms of temperature distribution and surface finish. Results shows that surface roughness and heat penetration were decreased with addition of Al2O3 nanoparticles. Keywords: Grinding; Al2O3 nanoparticle; Temperature distribution; Surface roughness; EN-31 steel Citation: V. Vasu and K. Manoj Kumar, “Analysis of Nanofluids as Cutting Fluid in Grinding EN-31 Steel”, Nano-Micro Lett. 3 (4), 209-214 (2011). http://dx.doi.org/10.3786/nml.v3i4.p209-214 Introduction Grinding is an abrasive material removal process, which is widely used in manufacturing compoents re- quiring fine tolerances and smooth finishes. Grinding process generates extreme heat and high cutting forces at workpiece wheel interface [1]. Cooling and lubrica- tion are necessary to protect the workpiece and wheel from workpiece burn, phase transformations, undesir- able residual tensile stresses, cracks, reduced fatigue strength, and thermal distortion and inaccuracies [1-2]. When the cutting fluid is applied to the grinding zone, it will initially undergo nucleate boiling, which enhances the rate of heat transfer between the workpiece and the fluid. As the temperature increases further, a vapour film is developed between the workpiece and the fluid, which acts as an insulator and prevents heat transfer to the fluid. As a result, the workpiece temperature quickly rises and burns the surface of the material [3]. An alternative to flood cooling is Minimum Quan- tity Lubrication (MQL) or use of Solid Lubricants. MQL gives similar results as that of flood cooling if the coolant in MQL does not evaporate due to the grinding heat [4]. Solid lubricants demonstrates sat- isfactory properties in grinding due to sustain of high temperature, nontoxic, easy to apply and cost effec- tive [5,6]. Instead of good results of solid lubrication, there is still a need for flushing action and tool clean- ing make less attractive than conventional liquid lu- brication methods. Due to emerging of nanotechnol- ogy, high thermal conducting fluids called ‘Nanofluids’ has emerged. Nanofluids are engineered colloidal sus- pension of nanoparticles (10∼100 nm) in base fluids [7]. The applicability of the fluids as coolants is mainly due to the enhanced thermo-physical properties of flu- ids due to the nanoparticles inclusion [8]. In this paper the effect on surface roughness and heat dissipation by suspending Al 2 O 3 nanoparticles in eco-friendly emulsifier TRIM E709 in machining EN-31 steel at different speed-feed-depth of cut combinations are observed. 1 Asst. Professor, Department of Mechanical Engineering, National Institute of Technology Warangal 506004, India 2 Research Scholar, Department of Mechanical Engineering, National Institute of Technology Warangal 506004, India *Corresponding author. E-mail: [email protected], [email protected]Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
Transcript
www.nmletters.org
Analysis of Nanofluids as Cutting Fluid in
Grinding EN-31 Steel
V. Vasu1,∗, K. Manoj Kumar2,∗
(Received 13 August 2011; accepted 22 September 2011; published online 3 November 2011.)
Abstract: Grinding requires high specific energy which develops high temperatures at wheel work piece
interface. High temperatures impair work piece quality by inducing tensile residual stress, burn, and micro
cracks. Control of grinding temperature is achieved by providing effective cooling and lubrication. Conven-
tional flood cooling is often ineffective due to enormous heat generation and improper heat dissipation. This
paper deals with an investigation on using TRIM E709 emulsifier with Al2O3 nanoparticles to reduce the heat
generated at grinding zone. An experimental setup has been developed for this and detailed comparison has
been done with dry, TRIM E709 emulsifier and TRIM E709 emulsifier with Al2O3 nanoparticles in grinding
EN-31 steel in terms of temperature distribution and surface finish. Results shows that surface roughness and
heat penetration were decreased with addition of Al2O3 nanoparticles.
Keywords: Grinding; Al2O3 nanoparticle; Temperature distribution; Surface roughness; EN-31 steel
Citation: V. Vasu and K. Manoj Kumar, “Analysis of Nanofluids as Cutting Fluid in Grinding EN-31 Steel”,
Nano-Micro Lett. 3 (4), 209-214 (2011). http://dx.doi.org/10.3786/nml.v3i4.p209-214
Introduction
Grinding is an abrasive material removal process,which is widely used in manufacturing compoents re-quiring fine tolerances and smooth finishes. Grindingprocess generates extreme heat and high cutting forcesat workpiece wheel interface [1]. Cooling and lubrica-tion are necessary to protect the workpiece and wheelfrom workpiece burn, phase transformations, undesir-able residual tensile stresses, cracks, reduced fatiguestrength, and thermal distortion and inaccuracies [1-2].When the cutting fluid is applied to the grinding zone, itwill initially undergo nucleate boiling, which enhancesthe rate of heat transfer between the workpiece and thefluid. As the temperature increases further, a vapourfilm is developed between the workpiece and the fluid,which acts as an insulator and prevents heat transferto the fluid. As a result, the workpiece temperaturequickly rises and burns the surface of the material [3].
An alternative to flood cooling is Minimum Quan-
tity Lubrication (MQL) or use of Solid Lubricants.MQL gives similar results as that of flood cooling ifthe coolant in MQL does not evaporate due to thegrinding heat [4]. Solid lubricants demonstrates sat-isfactory properties in grinding due to sustain of hightemperature, nontoxic, easy to apply and cost effec-tive [5,6]. Instead of good results of solid lubrication,there is still a need for flushing action and tool clean-ing make less attractive than conventional liquid lu-brication methods. Due to emerging of nanotechnol-ogy, high thermal conducting fluids called ‘Nanofluids’has emerged. Nanofluids are engineered colloidal sus-pension of nanoparticles (10∼100 nm) in base fluids[7]. The applicability of the fluids as coolants is mainlydue to the enhanced thermo-physical properties of flu-ids due to the nanoparticles inclusion [8].
In this paper the effect on surface roughness andheat dissipation by suspending Al2O3 nanoparticles ineco-friendly emulsifier TRIM E709 in machining EN-31steel at different speed-feed-depth of cut combinationsare observed.
1Asst. Professor, Department of Mechanical Engineering, National Institute of Technology Warangal 506004, India2Research Scholar, Department of Mechanical Engineering, National Institute of Technology Warangal 506004, India*Corresponding author. E-mail: [email protected], [email protected]
Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
Synthesis of Nanofluid
Alumina nanoparticles are prepared by LiquidPhase Synthesis [9] of Ammonium Aluminum Car-bonate Hydroxide (AACH) followed by thermal de-
composition (calcination). Then, nanofluid is pre-pared by mixing Al2O3 nanoparticles into an emul-sifier TRIM E709 by stirring for about 8 hourscontinuously using magnetic stirrer as shown inFig. 1(c).
Grinding Wheel
Depth of Cut Controller
Workpiece
Auto Feed Controller
Temperature Indicator
(a) Photographic view of the experimental setup (b) Temperature indicator
(c) Magnetic stirrer (d) TRIM E709 Emulsifier (e) EN-31 Steel work piece
Holes of Thermocouples 120
mm
100 mm120 m
m
Fig. 1 Experimental Setup and its apparatus.
Experimental procedure
Figure 1 shows the experimental setup for presentstudies, an EN-31 steel block of initial 100*120*120mm3 is machined using LAMBA grinding machineat different speed-feed-depth of cut combinations (seeTable 1&2) under dry condition, wet (emulsifier TRIME709) condition and emulsifier TRIM E709 with 1%Al2O3 nanofluid condition to study the role of Al2O3
nanoparticles on the machinability characteristics of thework material mainly in respect of surface roughnessand heat dissipation. The total number of experimentsaccording to full factorial design was 9, by taking feedand depth of cut at three levels for three different envi-ronments. The design of experiments for the full facto-rial design is shown in Table 3. Temperature measure-
ment is done by using J-Type thermocouples which areincorporated at a distance of 5 mm from all the edgesof the workpiece as shown in the Fig. 1(e).
Table 4 shows experimental results for surface rough-ness, wheel work piece interface temperature under dif-ferent environment conditions. From results as shownin Table 4, it is found that emulsifier+Al2O3 nanoparti-cles shows reduction in surface roughness and interfacetemperature than dry and plain emulsifier conditions.
Table 1 Control Factors and their levels.
Control FactorsLevels of factors
1 2 3
Feed (mm/sec) 100 150 200
Depth of cut (microns) 25 50 75
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Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
A finite model is proposed by considering the grind-ing wheel as a rectangular heat source of length equalto geometrical contact length Lc, between the grindingwheel and the workpiece as shown in Fig. 2. The heatsource moves along the surface of the workpiece at aspeed equal to the work speed along the grinding zone,Lc is calculated using Eq. (1).
Lc =√
dw × d (1)
wheel
Vw
Vwp
Lc
dw
d
workpiece
y
xL
h
Fig. 2 Nomenclature of grinding process.
The heat generated in the grinding zone during wetgrinding is transferred into the chip, grinding fluid,
wheel, and workpiece. Length of heat input is half ofthe length of contact [2] given as
Lh =Lc
2(2)
Cooling is simulated by means of convective bound-ary conditions. Top surface with a convective heattransfer coefficient of coolant, sides and bottom surfaceswere given convective heat coefficient of air (h=11.43w/m2k).
PLANE55 (2D, Quadrilateral, 4-node) element isused to mesh the workpiece, having more density atmachining area and decrease as move away from thecutting zone, for better distribution of temperature andalso to reduce computational time. The mesh details ofworkpiece for different depth of cuts 25μm, 50 μm and75 μm as shown in Table 5.
Table 5 Meshing of elements at different depth of
cut.
S.No Depth of Cut in μm No. of Nodes No. of Elements
1. 25 2236 2125
2. 50 1196 1125
3. 75 1326 1250
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Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
The top surface is applied with a heat transfer coef-ficient calculated from Reynolds, Prandtl and Nusseltnumbers and the remaining three surfaces were appliedwith air convection. The convective heat transfer co-efficient for nanofluids was calculated by using equa-tion (3) and thermo-physical properties of nanoparticleand base fluid as given in Table 6. The thermophysicalproperties of Nanofluids [10] is calculated by using theequations (5-7).
The heat transfer coefficient of nanofluid for flow overa flat plat can be calculated as
Turbulent Flow:
Nunf = 0.453Re0.5nf Pr0.333
nf
Laminar Flow:
Nunf = 0.332Re0.5nf Pr0.333
nf (3)
where, Renf and Prnf defined as
Renf =ρV L
nf
μnf
, P rnf =cnfμnf
knf
(4)
The density, specific heat and viscosity of nanofluidsare
ρnf = φρkp + (1 − φ)ρf (5)
Cp,nf =φ(ρcp)p + (1 − φ)(ρcp)f
ρnf
(6)
μnf = μf (1 + 39.11φ2 + 533.9φ2) (7)
where, φ is particle volume fraction and subscripts nf, p
and f correspond to nanofluid, particle, and base fluid,respectively.
Results and Discussions
Figure 3 shows the variation of temperature andFig. 4 shows surface roughness for different coolant en-vironments under different feed and depth of cut combi-nations. The variations of surface roughness and inter-face temperature variation for different control factorsand cutting environments are discussed below.
Fig. 4 Variation of Surface Roughness for different cutting environments.
Dry Wet 1% Al2O3
Dry Wet 1% Al2O3
Dry Wet 1% Al2O3
Fig. 5 Temperature distribution (a) for feed=200 mm/sec, depth of cut=25 μm (first row) (b) for feed=150 mm/sec, depthof cut=50 μm (second row) (c) for feed=100 mm/sec, depth of cut=75 μm (third row).
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Nano-Micro Lett. 3 (4), 209-214 (2011)/ http://dx.doi.org/10.3786/nml.v3i4.p209-214
Wheel Workpiece Interface Temperature
The major part of the work regarding temperature inmetal cutting has been focused on the wheel-workpieceinterface temperature (cutting temperature), this beingdue to the wear of grinding wheel and quality of worksurface etc., as wear is sensitive to the cutting tempera-ture in metal cutting zone. From Fig. 3 effect of dry ma-chining, emulsifier and emulsifier +1% Al2O3 nanopar-ticles on wheel-workpiece interface temperature underdifferent feed rate and OK the increase in depth of cutand feed rate, average wheel-workpiece interface tem-perature increases as usual due to increase in cuttingenergy input. However, it is also seen the interface tem-peratures generated decreases in emulsifier +1% Al2O3
nanofluid condition as compared to dry and plain emul-sified condition. This can be due to higher thermo phys-ical properties of emulsifier +Al2O3 nanofluid.
Surface Roughness
Surface roughness of the work piece was measured byTaylor-Hobson surtronic 3+ talysurf with resolution of0.01 μm, traverse length of 0.25 mm and traverse speedof 1 mm/sec. Figure 4 indicates that increase in surfaceroughness with increase in feed rate and also increas-ing in surface roughness with increase in depth of cut.The reduction in surface roughness was observed to be35% to 40% in emulsifier + 1 % Al2O3 nanoparticlescondition. This can be due to more intensive temper-ature generated in grinding zones, results in the devel-opment of residual stresses, micro-cracking and tem-pering of the work piece surface, which decrease in byadding Al2O3 nanoparticles results in increase of ther-mal conductivity and heat transfer coefficient of emul-sified nanofluid compared to the plain emulsifier.
Temperature Distribution
The FEM heat transfer model has been used to esti-mate the energy partition OK in the real grinding appli-cation. The FEM heat transfer model traces the tem-poral distribution of the temperature in the workpiece,rather than only a steady-state solution. Therefore,the temperature response measured by thermocouple,which is in the time domain can be matched to FEMheat transfer model for energy partition in workpiece.Figure 5 indicates that energy partition is reduced inemulsifier + Al2O3 nanofluid when compared to dryand plain emulsifier.
Conclusion
Due to the enormous amount of heat energy gener-ated at the grinding zone, in order to avoid thermaldamage to workpiece, a new cutting fluid, TRIM E709emulsifier with Al2O3 nanoparticles, has been devel-oped to enhance heat transfer in grinding EN-31 steel.The major conclusions from this investigation can besummarized as follows:
• By using TRIM E709 emulsifier with Al2O3
nanoparticles the wheel-workpiece temperaturesare reduced by 20 to 30% compared to dry andplain emulsifier.
• Surface finish also significantly improved mainlydue to reduction in wear and damage at the wheelsurface by the application of TRIM E709 emulsi-fier with Al2O3 nanoparticles.
• FEM grinding model has been used to simulateenergy partition in dry, plain emulsifier and emul-sifier with 1% Al2O3 nanofluid in grinding of EN-31 steel and we found decrease in energy parti-tion and surface roughness with addition of Al2O3
nanoparticles.
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